Summary: Six titanomagnetites from a differentiated alkaline intrusion have been studied using mieroscopie, chemical, and X-ray techniques. The titanomag-netites are homogeneous; with differentiation their FeO and TiO2 contents decrease, and Fe2O3 increases. The titanomagnetite course of crystallization extends from close to the ulvöspinel-magnetite join, near to ulvöspinel, towards magnetite. The recalculated normative compositions of three titanomagnetites indicate that they are essentially Fe3O4-(γ-FeTiO3)-(γ-Fe2O3)solid solutions. The changing chemistry of the titanomagnetites is ascribed primarily to variations in the chemistry of the magma during differentiation.